Source: Flickr user Sean MacEntee.

The biopharmaceutical realm is a world filled with numerous hits and misses. But if you imagine the sphere of hits versus the sphere of misses, you're probably comparing something the size of a basketball (the hits) to an object the size of the Earth (the misses).

The drug development process for biopharmaceutical companies is long, arduous, costly, and it rarely ends with success. According to MedScape, just one out of every 5,000-10,000 drugs being tested in preclinical trials will ever make it to pharmacy shelves. That's a pretty poor success rate, but the drug development guidelines put in place by the Food and Drug Administration are there for a reason: to ensure patients get life-changing products that are both safe and effective.

A handful of big hits
Of course, if a drug winds up being approved by the FDA the rewards can be enormous. Pfizer's (PFE 1.22%) cholesterol-fighting drug Lipitor is the world's best-selling drug of all time, raking in $131 billion in cumulative sales according to FierceBiotech's data on the drug from a few years ago. Despite being off patent in the U.S., Lipitor continues to find success overseas and in other combinations within the U.S., further adding to its all-time sales lead.

Source: Flickr user Damian Gadal.

AbbVie's (ABBV 0.22%) anti-inflammatory Humira is another great example. Humira is currently approved in eight separate indications by the FDA, spanning back to its first approval all the way in 1999. This year, Humira is on pace for as much as $12 billion in global sales after crossing $10 billion in sales last year.

But, what if I said there was a drug out there which also had $10 billion-plus annual sales potential and that it wouldn't take a decade or longer to reach that $10 billion. In fact, it may not even take a year to reach $10 billion in sales. I'm talking about a drug that could very easily become the quickest ever to ramp up to blockbuster status. Sound intriguing? If so, then feast your eyes upon Gilead Sciences (GILD 0.61%) latest FDA approved drug to treat hepatitis C, Harvoni.

Could this drug deliver $10 billion in sales in its first year?
Late last week Gilead Sciences announced that the FDA had approved its hepatitis C "cocktail" drug Harvoni, a combination of FDA-approved Sovaldi with ledipasvir into a once-daily tablet.

Source: Gilead Sciences.

Right now you might be wondering why this approval is such a big deal in the first place if Gilead already has Sovaldi approved to treat hepatitis C. The answer to that question is that Sovaldi was approved to be used without interferon, which comes with nasty flu-like side effects for most patients, in genotype 2 and 3 patients, but still had to be taken with interferon in genotype 1 patients. The ability to ditch interferon in the administration of the drug was Sovaldi's great selling point, but genotype 1 is by far the most common form of hepatitis C.

Enter Harvoni, which as a combination tablet can treat genotype 1 patients without the need for either interferon or a ribavirin. In other words, many of the adverse effects of treating hepatitis C have been thrown out the window.

But, Harvoni is more than just a fancy new tablet that will lessen treatment side effects. In the three clinical studies that led to its approval, it was noted that the sustained virologic response after 12 weeks of treatment, or SVR12, was an astounding 94% to 99% in the ribavirin-free arms. To put it another way, Harvoni is curing in the neighborhood of 19 out of every 20 genotype 1 patients, and genotype 1 is the most difficult to treat.

Furthermore, Harvoni can be administered in some instances to treatment-naïve patients with or without cirrhosis of the liver over the course of just eight weeks as opposed to 12 weeks. This means potentially quicker treatment times, faster results, and of course less cost to the patient.

Source: Flickr user Ano Lobb.

Though, it should be noted that Harvoni will run $1,125 per pill, up 12.5% from the $1,000 per-pill price for Sovaldi that's had patients, insurers, and Congress up in arms. For those patients that are treatment-experienced and have cirrhosis of the liver, they'll still be facing a standard 24-week treatment course, or a whopping $189,000 total cost for treatment.

So how exactly is Harvoni going to reach $10 billion in sales in four quarters or less?  Just take a closer look at Sovaldi's track record for inspiration. Following its approval in Dec. 2013, Sovaldi managed to rack up $2.27 billion in Sovaldi sales in the first quarter, and an additional $3.48 billion in sales in the second quarter. Through six months Sovaldi was on pace to give Humira a run for its money with $5.75 billion in cumulative sales.

The kicker is that Harvoni is a better drug than Sovaldi will ever be, making it the clear choice to garner the bulk of hepatitis C sales. This means, at least until new competition emerges from the likes of AbbVie with its direct-acting antiviral (DAA) combo drug, that Johnson & Johnson's (JNJ 0.27%) Olysio, which has brought in around $2 billion in sales this year, and Gilead's own Sovaldi are likely to see their sales slump in rapid fashion as Harvoni ramps up.

Keep this in mind
Of course, investors would be wise to keep two factors in mind. First, hepatitis C competition is only going to increase, with AbbVie expected to gain approval for its DAA soon and Merck (MRK -0.60%) pushing forward with its combo drugs, MK-5172 and MK-8472, in clinical studies. Further, Merck's $3.85 billion purchase of Idenix could yield a number of unique or combination therapies involving Idenix's nucleotide-based drugs.

Secondly, I could be wrong. I've been wrong before and I'll be wrong at some point again. Only you are in the driver seat of your investment portfolio, which means you have to make the decision as to whether Gilead Sciences can trek higher from here based on sales of Harvoni. A mix of competition, Congressional pricing pressures, or even too many hepatitis C patients taking the drug for eight weeks instead of 12 could adversely impact its sales potential.

If you were to ask me, however, I believe you're about to witness something truly special with Harvoni.